If the Desktop Sync
client connects to Alfresco Content Services to start content selection then immediately goes offline, folders
may already have been created, but no files have been synced; check
the following:

The Sync Service is running

The Sync Service is accessible from the client - you can use the Healthcheck URL in the clients browser

For example, if the Sync Service port is not open on the firewall,
then the client won't be able to connect to the Desktop Sync
service, or the Healthcheck URL. The port is set when Installing Sync Service,
where the default is 9090.

What can I check
if content can't be added to or updated in Alfresco Content
Services via Alfresco Share or another application?

To fix this issue,
check if ActiveMQ is running and available to the repository. See
Prerequisites and supported platforms for more. A feature of the Sync Service is to provide resilience of the service, and ensuring that no
critical event information is lost.

The recommendation is to
run an ActiveMQ cluster to ensure high availability.

Why has sync
stopped working since upgrading the client operating system
(for example to Mac OS X to Sierra High)?

If SSL
has been enabled on the Sync Service without provision for a signed certificate, then the clients may
fail to sync content. The log files contain a message "SSL peer
certificate or SSH remote key was not OK".
Install the Sync Service with a valid security certificate or disable SSL
for the synchronization server if required.

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